The present invention relates to an arrangement connecting a vehicle brake disc on a carrier and for providing relative movement between them.
The invention thus concerns an arrangement for releasable fastening of an annular vehicle brake disc to a rotatable carrier which supports the brake disc. The carrier may be a wheel hub or a sleeve-shaped extension which is fastened to and protrudes axially from a wheel hub. The internal periphery of the brake disc is provided with driving protrusions which are separated in the circumferential direction, face radially inwards towards the centre of the disc and engage in a corresponding number of external axial grooves between ridges which run axially on the outside of the carrier. In other words, the brake disc is fitted to the carrier by means of a splined connection.
Vehicle brake discs which are fitted to and rotate jointly with a wheel hub provided with external splines, or some other kind of brake disc carrier, have a definite tendency to gradually rust fast to the wheel hub or carrier after certain time in operation on a vehicle. This may often result in it being very difficult or totally impossible to detach brake discs from the hub or carrier. There has hitherto been no easy and reliable way of solving this well-known problem of rusted-on brake discs.
An example of known technology which may be cited with regard to brake disc fastening is international patent publication WO 97/20151 (PCT/EP96/04948) which describes a brake disc/hub connection whereby a brake disc is releasably connected to a wheel hub, particularly in the case of disc brakes of commercial vehicles. The internal periphery region of the brake disc is provided with supporting elements, and the wheel hub has chambers on its outer periphery. At the same time, special intermediate elements are arranged for torque and force transmission from the hub""s chambers to the brake disc""s supporting elements. The intermediate elements are so designed that the wheel hub""s chambers engage in them. The intermediate elements engage in turn in the supporting elements and their shape results in their bearing, in the circumferential direction, on the supporting elements. The chambers are also connected by shape and/or force to the intermediate elements. However, this relatively complicated type of connection arrangement between brake disc and hub does not solve the rusting-on problem in an entirely reliable manner, nor does it afford the manufacturing advantages of a splined connection.
The object of the invention is to solve the aforesaid problem, which arises when trying to remove brake discs, by providing a new type of brake disc fastening which effectively eliminates the risk of brake discs rusting fast such that it becomes impossible or extraordinarily difficult to detach them from the carrier or hub.
For, among others, service and maintenance reasons, it is extraordinarily important to be able to carry out necessary brake disc changing quickly and easily and without needing special tools.
The aforesaid object is achieved according to the invention by an arrangement including a brake disc on a carrier as described above, with a measure to avoid the effect of rusting.
A primary distinguishing feature of the fastening arrangement according to the invention is that the brake disc""s driving protrusions are of smaller extent in the circumferential direction of the carrier than the width of the grooves in their circumferential direction, so that it is possible for there to be between adjacent sets of mutually engaging driving protrusions and grooves a spacing gap to accommodate a spacing device removably fastened therein. This spacing device is so designed as to fit into and fill the spacing gap and hence fix the brake disc relative to the carrier. At its axially opposite ends the spacing device is also provided with shoulder portions to prevent mutual axial movement between the brake disc and the carrier (the hub).
When the time comes to replace the brake disc fitted to the carrier with a new brake disc and rusting-on (xe2x80x9cchemical rust connectionxe2x80x9d) is found to have occurred between the brake disc and the spacing devices inserted in the gaps between the driving protrusions and the carrier grooves, the first step is to remove the shoulder portions at one end of the spacing devices. Thereafter the spacing devices can be removed without difficulty from the spacing gaps between the brake disc driving protrusions and the carrier ridges.
The fastening arrangement according to the invention may further afford various functional and manufacturing advantages.
For both fitting and removal of the spacing devices to be easy to carry out, it may be advantageous to adopt a version whereby each spacing device incorporates not only a preferably substantially T-shaped spacing element with a stem and a transverse head which constitutes one of the two shoulder portions and is intended to abut against a first side of the brake disc and the carrier, but also a shoulder element which is fastenable in the stem of the spacing element, comprises the second shoulder portion and is intended to abut against an opposite second side of the brake disc and the carrier.
Removing a spacing device, i.e. extracting the device from the spacing gap in which it is inserted, involves first detaching the shoulder element from the stem of the spacing element, followed by removing the spacing element from the spacing gap.
A particularly simple version is distinguished by the T-shaped spacing element having a hollow stem which is substantially prismatic or cylindrical on the outside and by the fastenable shoulder element consisting of a locking screw which is screwable into the hollow stem of the spacing element and which has a screw head which constitutes the second shoulder portion. In this case the two shoulder portions of the spacing device are thus respectively the transverse T-head of the spacing element and the head of the locking screw.
To optimise the possibility of detaching the spacing device from the spacing gap even when the spacing device has rusted fast to the brake disc, it may be particularly advantageous for the hollow stem of the spacing element to be split axially into two parallel stem halves which may then be pressed together when the locking screw has been removed (unscrewed) from the hollow stem of the spacing element. Pressing the stem halves together has the effect of somewhat reducing the transverse dimension of the stem, thus greatly facilitating the removal of the spacing element from the spacing gap.
To reduce the risk of the locking screw rusting fast in the hollow shaft of the spacing element, it may be advantageous for the locking screw to have a stem with external thread on only the outermost portion of the length of the stem, and for the spacing element to be provided with a corresponding internal thread on only its transverse T-head.
As an alternative to a spacing element with a hollow stem and a locking screw screwable into it, a version is also conceivable whereby the fastenable shoulder element takes the form of a cylindrical pin which is screwable into the hollow stem of the spacing element and which is provided, in its outer end situated outside the outside of the brake disc/carrier, with a positionally fixed locking device which then constitutes the second shoulder portion. This locking device may for example be a split-pin running through the pin, or a locking ring or lock washer inserted in a circumferential recess on the outside of the end of the cylindrical pin.
To minimise any risk of the spacing devices rusting fast to the brake disc, it is of course best of all if both the spacing element and the shoulder element fastenable in it are made of a material which tends not to rust, e.g. stainless steel.